Abstract:

An exemplary device for controlling rotation speed of a computer fan
includes an identifying device and a control circuit. The identifying
device is configured for identifying the type of the computer fan. The
control circuit configured for controlling rotation speed of the computer
fan includes an electric switch, an integrated circuit, a first output
terminal, and a second output terminal. The electric switch has a first
terminal coupled to the identifying device to receive an identifying
signal, a second terminal coupled to a super I/O chip to receive a PWM
signal. The integrated circuit is configured to convert the PWM signal to
an analog voltage signal. The first output terminal is configured to
output the PWM signal to a PWM control pin of a fan header. The second
output terminal is configured to output the analog voltage signal to a
power pin of the fan header.

Claims:

1. A device for controlling rotation speed of a computer fan comprising:an
identifying device configured for identifying the type of a computer fan,
comprising a switch having a control terminal and a ground terminal, the
control terminal connected to a power supply via a resistor, the ground
terminal grounded; anda control circuit configured for controlling
rotation speed of the computer fan comprising:an electric switch having a
first terminal coupled to a node between the first resistor and the
control terminal to receive an identifying signal generated by the
identifying device, a second terminal coupled to a super input/output
(I/O) chip to receive a pulse-width modulation (PWM) signal, and a third
terminal;an integrated circuit having an input terminal connected to the
third terminal of the electric switch, and an output terminal configured
to output an analog voltage signal;a first output terminal connected to
the super I/O chip, configured to output the PWM signal to a PWM control
pin of a fan header; anda second output terminal configured to output the
analog voltage signal to a power pin of the fan header.

2. The control device as claimed in claim 1, wherein the switch is
vertically mounted on the fan header at a side of pins thereon, the
ground terminal is a sheet of metal, and the control terminal is a sheet
of metal having a V-shaped upper portion with an opening towards the
ground terminal.

3. The control device as claimed in claim 1, wherein the switch is mounted
on the fan header at a side of pins thereon, the control terminal is a
sheet of metal having an inverted V-shaped middle portion, two flanges
extend outwardly and upwardly from lateral free ends of the middle
portion, one flange is fixed on the fan header, the other flange forms a
free end facing the PWM control pin, and the ground terminal is a sheet
of metal located on the fan header under the free end of the control
terminal.

4. The control device as claimed in claim 1, wherein the integrated
circuit comprises a resistor and a capacitor connected in series between
the input terminal of the integrated circuit and ground, and a node
between the resistor and the capacitor acts as the output terminal of the
integrated circuit.

5. The control device as claimed in claim 1, wherein the control circuit
further comprises a linear voltage regulating circuit, the linear voltage
regulating circuit comprises an input terminal connected to the output
terminal of the integrated circuit to receive the analog voltage signal,
and an output terminal connected to the power pin of the fan header to
output a corresponding voltage signal to the power pin.

6. The control device as claimed in claim 1, wherein the fan header is a
4-pin fan header.

7. The control device as claimed in claim 5, wherein the linear voltage
regulating circuit further comprises an amplifier and a transistor, a
negative terminal of the amplifier acts as the input terminal of the
linear voltage regulating circuit, a positive terminal of the amplifier
is connected to the collector of the transistor via a resistor, an output
of the amplifier is connected to the base of the transistor via a
resistor, and the collector of the transistor acts as the output terminal
of the linear voltage regulating circuit.

8. The control circuit as claimed in claim 6, wherein the transistor is a
PNP transistor.

9. The control circuit as claimed in claim 6, wherein the base of the
transistor is connected to the emitter of the transistor via a resistor.

10. The control device as claimed in claim 1, wherein the second and third
terminals of the electric switch are connected to a power supply via a
resistor.

11. The control device as claimed in claim 1, wherein the electric switch
is an NMOS transistor, the first, second, and third terminals are the
gate, the source, and the drain of the NMOS transistor respectively.

Description:

BACKGROUND

[0001]1. Field of the Invention

[0002]The present invention relates to computer fans, and particularly to
a device for controlling rotation speed of a computer fan.

[0003]2. Description of Related Art

[0004]Generally, a computer system includes a motherboard with various
chips such as a central processing unit (CPU) mounted thereon, a storage
device such as a hard disc, and input/output devices. Many of these
devices generate heat when the computer system is operating, particularly
the CPU. If the heat generated from the CPU is not dissipated in a timely
fashion, it may damage the CPU or even other parts of the computer
system.

[0005]Typically, a sensor is programmed to be used as a temperature
detector for detecting temperature of the CPU. A computer fan is used to
facilitate removal of heat to keep the temperature of the CPU within a
safe temperature range. A fan controller is provided to adjust fan speed
to be more energy efficient while still providing enough heat
dissipation. The computer fan includes 3-pin fans, which can be adjusted
by a voltage signal and 4-pin fans, which can be adjusted by a
pulse-width modulation (PWM) signal controlled by a basic input/output
system (BIOS) of the motherboard.

[0006]In a 3-pin fan motherboard, a 3-pin fan is connected to the
motherboard by a 3-pin fan header mounted on the motherboard, and a 3-pin
fan controller is used to provide the voltage signal to the 3-pin fan for
adjusting the rotation speed of the 3-pin fan. In a 4-pin fan
motherboard, a 4-pin fan is connected to the motherboard by a 4-pin fan
header mounted on the motherboard, and a 4-pin fan controller is used to
provide the PWM signal to the fourth pin of the 4-pin fan for adjusting
the rotation speed of the 4-pin fan. In theory, the 3-pin fan can be
connected to the 4-pin fan motherboard by the 4-pin fan header. However,
the 3-pin fan cannot be controlled by the 4-pin fan controller because
the 3-pin fan does not have the fourth pin and cannot receive the PWM
signal from the 4-pin fan controller. Therefore, the CPU of the 4-pin fan
motherboard may be damaged because the heat may not be dissipated
properly.

[0007]What is needed, therefore, is to provide a device which can identify
the type of a computer fan in use and adjust the rotation speed of the
computer fan, whether it be a 3-pin fan or a 4-pin fan.

SUMMARY

[0008]An exemplary device for controlling rotation speed of a computer fan
includes an identifying device and a control circuit. The identifying
device configured for identifying the type of the computer fan, includes
a switch having a control terminal and a ground terminal, the control
terminal connected to a power supply via a resistor, the ground terminal
grounded. The control circuit configured for controlling rotation speed
of the computer fan includes an electric switch, an integrated circuit, a
first output terminal, and a second output terminal. The electric switch
has a first terminal coupled to a node between the first resistor and the
control terminal to receive an identifying signal generated by the
identifying device, a second terminal coupled to a super input/output
(I/O) chip to receive a pulse-width modulation (PWM) signal, and a third
terminal. The integrated circuit has an input terminal connected to the
third terminal of the electric switch, and an output terminal configured
to output an analog voltage signal. The first output terminal is
connected to the super I/O chip, and is configured to output the PWM
signal to a PWM control pin of a fan header. The second output terminal
is configured to output the analog voltage signal to a power pin of the
fan header.

[0009]Other novel features and advantages will become more apparent from
the following detailed description of preferred and exemplary embodiments
when taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is an isometric view of a switch installed on a 4-pin fan
header in accordance with an embodiment of the present invention;

[0011]FIG. 2 is a circuit diagram of a device for controlling rotation
speed of a computer fan in accordance with an exemplary embodiment of the
present invention; and

[0012]FIG. 3 is an isometric view of a switch installed on the 4-pin fan
header in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION

[0013]Referring to FIG. 1 and FIG. 2, a device for controlling rotation
speed of a computer fan in accordance with an embodiment includes an
identifying device 10 and a control circuit 40. The identifying device 10
includes a power supply VCC, a resistor R, and a switch 20 having a
control terminal 22 and a ground terminal 24. The control circuit 40
includes an electric switch Q1, an integrated circuit (IC) 50 having a
resistor R1 and a capacitor C1, a linear voltage regulating circuit 60
having an amplifier U and a transistor Q2 functioning as a current
controller, a first output terminal M1, and a second output terminal M2.
In this embodiment, the electric switch Q1 is a
negative-metal-oxide-semiconductor (NMOS) transistor, and the transistor
Q2 is a positive-negative-positive (PNP) transistor. Typically, the
computer fan is connected to a motherboard of a computer by a fan header
mounted on the motherboard.

[0014]The switch 20 is mounted on a 4-pin fan header which includes a
baseplate 5 mounted on the motherboard, and four pins 1˜4 mounted
on the baseplate 5 and connected to the motherboard. The ground terminal
24 is a sheet of metal and is vertically mounted on the baseplate 5 at
the right side of a PWM control pin 4. The control terminal 22 is a sheet
of metal and is vertically mounted on the baseplate 5 between the PWM
control pin 4 and the ground terminal 24, has a V-shaped upper portion
with an opening toward the ground terminal 24, and is connected to the
power supply VCC via the resistor R.

[0015]The gate of the NMOS transistor Q1 is coupled to a node between the
resistor R and the control terminal 22 to receive an identifying signal
generated by the identifying device 10. The source of the NMOS transistor
Q1 is coupled to a super input/output (I/O) chip to receive a pulse-width
modulation (PWM) signal, and is coupled to a 5V power source via a
resistor R7. The drain of the NMOS transistor Q1 is connected to the 5V
power source via a resistor R6, and is grounded via the resistor R1 and
the capacitor C1. In other embodiments, the 5V power source, the resistor
R6, and the resistor R7 can be omitted. The amplifier U includes a
negative input terminal connected to a node between the resistor R1 and
the capacitor C1 to receive an analog voltage signal therefrom, a
positive terminal grounded via a resistor R2, an output terminal, and a
power terminal connected to a 12V power source. The base of the
transistor Q2 is connected to the output terminal of the amplifier U via
a resistor R4. The emitter of the transistor Q2 is connected to the 12V
power source, and is connected to the base of the transistor Q2 via a
resistor R8. The collector of the transistor Q2 is connected to the
positive terminal of the amplifier U via a resistor R3, and is grounded
via a capacitor C2. The first output terminal M1 is connected to the
super I/O chip via a resistor R5, configured to output the PWM signal to
the PWM control pin 4 of the 4-pin fan header. The second output terminal
M2 is connected to the collector of the transistor Q2, configured to
output the analog voltage signal to a power pin 2 of the 4-pin fan
header. The connection between the positive input terminal of the
amplifier U and the collector of the transistor Q2 forms a negative
feedback loop for steadying the circuit.

[0016]If a 4-pin fan connector 6 is mounted on the 4-pin fan header before
turning on the computer, the 4-pin fan connector 6 will press the upper
portion of the control terminal 22 to make the control terminal 22 abut
the ground terminal 24, closing the switch 20, and the identifying signal
generated by the identifying device 10 is at a low level to turn off the
NMOS transistor Q1. The PWM signal is directly transmitted to the PWM
control pin 4 of the 4-pin fan header by the first output terminal M1 to
control the rotation speed of the computer fan thereafter.

[0017]If a 3-pin fan connector (not shown) is mounted on the 4-pin fan
header before turning on the computer, the 3-pin fan connector will not
touch the control terminal 22 because the 3-pin fan connector has no PWM
control pin 4, and because the width of the 3-pin fan connector is
shorter than that of the 4-pin fan connector, the switch 20 remains open,
and the identifying signal generated by the identifying device 10 is at a
high level to turn on the NMOS transistor Q1. The PWM signal is
transmitted to the NMOS transistor Q1, and then is converted to an analog
voltage signal by the IC 50. The analog voltage signal is transmitted to
the negative input terminal of the amplifier U, and then the amplifier U
outputs an amplified voltage signal. The transistor Q2 works in an
amplification region. Therefore if the current of the base of the
transistor Q2 changes, the current change at the collector of the
transistor Q2 will change in direct proportion to the current change of
the base. Thus a corresponding change occurs to the voltage signal at the
collector of the transistor Q2. Because the change of the rotation speed
of the computer fan is in direct proportion to the change of the voltage
signal of the collector of the transistor Q2, the rotation speed of the
computer fan is thus controlled by the PWM signal.

[0018]Referring to FIG. 3, in another embodiment of the present invention,
the switch 30 includes a control terminal 32 and a ground terminal 34
mounted on the 4-pin fan header at the right side of the PWM control pin
4. The control terminal 32 is a sheet of metal having an inverted
V-shaped middle portion, two flanges extend outwardly and upwardly from
lateral free ends of the middle portion, one flange is fixed on the
baseplate 5, the other flange forms a free end facing the PWM control pin
4, and the control terminal 32 is connected to the power supply VCC via
the resistor R. The ground terminal 32 is a sheet of metal located on the
baseplate 5 under the free end of the control terminal 32, and grounded.

[0019]In the present embodiment, the identifying device 10 identifies the
type of the computer fan according to the state of the switch 30, and the
control circuit 40 automatically selects a corresponding circuit to
control the rotation speed of the fan according to an identifying signal
generated by the identifying device 10. When the 4-pin fan connector 6 is
connected to the 4-pin fan header, the 4-pin fan connector 6 will press
the free end of the control terminal 32 to downwardly touch the ground
terminal 34, closing the switch 30, and the identifying signal is at a
low level to turn off the NMOS transistor Q1, and the PWM signal is
directly transmitted to the PWM control pin 4 of the 4-pin fan header by
the first output terminal M1 to control the rotation speed of the
computer fan thereafter. When the 3-pin fan connector is connected to the
4-pin fan header, the switch 30 remains open, and the identifying signal
is at a high level to turn on the NMOS transistor Q1, and the PWM signal
is transmitted to the NMOS transistor Q1, then is converted to an analog
voltage signal transmitted to a power pin 2 of the 4-pin fan header by
the second output terminal M2 to control the rotation speed of the
computer fan.

[0020]It is to be understood, however, that even though numerous
characteristics and advantages of the present embodiments have been set
forth in the foregoing description, together with details of the
structures and functions of the embodiments, the disclosure is
illustrative only; and that changes may be made in detail, especially in
matters of shape, size, and arrangement of parts within the principles of
the invention to the full extent indicated by the broad general meaning
of the terms in which the appended claims are expressed.